Fri·Mar 9, 2018Friday·March 9, 2018

1. 01*

   Isospin influence on dynamical production of Intermediate Mass Fragments at Fermi Energies

   P. Russotto🇮🇹 · E. De Filippo🇮🇹 · E.V. Pagano🇮🇹 · L. Acosta🇮🇹 · L. Auditore🇮🇹 · T. Cap🇵🇱 · G. Cardella🇮🇹 · S. De Luca🇮🇹 · B. Gnoffo🇮🇹 · G. Lanzalone🇮🇹 · I. Lombardo🇮🇹 · C. Maiolino🇮🇹 and 17 other authors

   The Intermediate Mass Fragments emission probability from Projectile-Like Fragment break-up in semi-peripheral reactions has been measured in collisions of ${}^{124}$Xe projectiles with two different targets of ${}^{64}$Ni and ${}^{64}$Zn at the laboratory energy of 35 \amev. The two colliding systems differ only for the target atomic number Z and, consequently, for the Isospin $N/Z$ ratio. An enhancement of Intermediate Mass Fragments production for the neutron rich ${}^{64}$Ni target, with respect to the ${}^{64}$Zn, is found. In the case of one Intermediate Mass Fragment emission, the contributions of the dynamical and statistical emissions have been evaluated, showing that the increase of the effect above is due to an enhancement of the dynamical emission probability, especially for heavy IMFs (Z$\gtrsim$ 7). This proves an influence of the target Isospin on inducing the dynamical fragment production from Projectile-Like Fragment break-up. In addition, a comparison of the Xe+Ni,Zn results with the previously studied ${}^{112,124}Sn{+}^{58,64}Ni$ systems is discussed in order to investigate the influence of the projectile Isospin alone and to disentangle between Isospin effects against system-size effects on the emission probability. These comparisons suggest that the prompt-dynamical emission is mainly ruled by the $N/Z$ content of, both, projectile and target; for the cases here investigated, the influence of the system size on the dynamical emission probability can be excluded.

   nucl-ex2 citations
2. 02*

   On the Production of an Isotensor Dibaryon in the $pp\to pp{\pi }^{+}{\pi }^{-}$ Reaction

   P. Adlarson · W. Augustyniak · W. Bardan · M. Bashkanov · F.S. Bergmann · M. Berłowski · A. Bondar · M. Büscher · H. Calén · I. Ciepał · H. Clement · E. Czerwiński and 72 other authors

   Exclusive measurements of the quasi-free $pp\to pp{\pi }^{+}{\pi }^{-}$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p=1.08-1.36$ GeV ($\sqrt{s}$ = 2.35 - 2.46 GeV), which includes the regions of $N^{\ast }(1440)$ and $\Delta (1232)\Delta (1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P)=2(1^{+})$ produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more recently calculated by Gal and Garcilazo.

   nucl-exhep-exPRC(2019)·9 citations
3. 03*

   An Isotensor Dibaryon in the $pp\to pp{\pi }^{+}{\pi }^{-}$ Reaction?

   P. Adlarson · W. Augustyniak · W. Bardan · M. Bashkanov · F.S. Bergmann · M. Berłowski · A. Bondar · M. Büscher · H. Calén · I. Ciepał · H. Clement · E. Czerwiński and 72 other authors

   Exclusive measurements of the quasi-free $pp\to pp{\pi }^{+}{\pi }^{-}$ reaction have been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region $T_p=1.08-1.36$ GeV, which is the region of $N^{\ast }(1440)$ and $\Delta (1232)\Delta (1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P)=2(1^{+})$ produced associatedly with a pion is able to overcome these deficiencies.

   nucl-exhep-exPRL(2018)·26 citations
4. 04*

   Responses of the chiral-magnetic-effect-sensitive sine observable to resonance backgrounds in heavy-ion collisions

   Yicheng Feng🇺🇸 · Jie Zhao🇺🇸 · Fuqiang Wang🇺🇸

   A new sine observable, $R_{{\Psi }_2}(\Delta S)$, has been proposed to measure the chiral magnetic effect (CME) in heavy-ion collisions; $\Delta S=⟨\sin {\phi }_{+}⟩-⟨\sin {\phi }_{-}⟩$, where ${\phi }_{\pm }$ are azimuthal angles of positively and negatively charged particles relative to the reaction plane and averages are event-wise, and $R_{{\Psi }_2}(\Delta S)$ is a normalized event probability distribution. Preliminary STAR data reveal concave $R_{{\Psi }_2}(\Delta S)$ distributions in 200 GeV Au+Au collisions. Studies with a multiphase transport (AMPT) and anomalous-viscous Fluid Dynamics (AVFD) models show concave $R_{{\Psi }_2}(\Delta S)$ distributions for CME signals and convex ones for typical resonance backgrounds. A recent hydrodynamic study, however, indicates concave shapes for backgrounds as well. To better understand these results, we report a systematic study of the elliptic flow ($v_2$) and transverse momentum ($p_T$) dependences of resonance backgrounds with toy-model simulations and central limit theorem (CLT) calculations. It is found that the concavity or convexity of $R_{{\Psi }_2}(\Delta S)$ depends sensitively on the resonance $v_2$ (which yields different numbers of decay ${\pi }^{+}{\pi }^{-}$ pairs in the in-plane and out-of-plane directions) and $p_T$ (which affects the opening angle of the decay ${\pi }^{+}{\pi }^{-}$ pair). Qualitatively, low $p_T$ resonances decay into large opening-angle pairs and result in more `back-to-back' pairs out-of-plane, mimicking a CME signal, or a concave $R_{{\Psi }_2}(\Delta S)$. Supplemental studies of $R_{{\Psi }_3}(\Delta S)$ in terms of the triangular flow ($v_3$), where only backgrounds exist but any CME would average to zero, are also presented.

   ↳ nucl-thnucl-exPRC(2018)·20 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.